Computer system and method for migrating from one storage system to another

ABSTRACT

The present invention provides a method for migrating from a source storage system to a target storage system. The method comprises the steps of: defining a volume defined on a drive to be migrated in the source storage system as an external volume of the target storage system; causing the host to access the volume on the drive to be migrated through an input/output port of the drive to be migrated as the external volume of the target storage system; blocking the other input/output port of the drive to be migrated while maintaining the access to the external volume of the target storage system; reconnecting the blocked input/output port with an interface in the target storage system; blocking the input/output port through which the external volume is being accessed, and connecting it with the interface in the target storage system; and implementing the drive to be migrated in the target storage system. This method can be used to migrate data from the source storage system to the target storage system on a drive basis while receiving read/write requests for the data from the host computer and continuously using some of the source storage system.

CLAIMS OF PRIORITY

The present application claims prority from Japanese application serialno. 2004-208752, filed on Jul. 15, 2004, the content of which is herebyincorporated by reference into this application.

BACKGROUND

The present invention relates to a method for migrating from one storagesystem to another, and more particularly to a method for smoothlymigrating data from one storage system to another without shutting downthese systems.

Data migration techniques for moving data stored in one storage systemto another storage system are important in running a computer system towhich storage systems are connected. For example, when a new storagesystem is introduced, the data in the old storage system may need to bemoved to the new storage system.

Further, data may be moved from a storage system under high loadconditions to that under low load conditions while using these storagesystems. Data migration may be carried out not only between storagesystems but also between storage devices in a storage system.

U.S. Pat. No. 6,108,748 discloses a technique of migrating data from onestorage system to another transparently to the host while maintainingaccess by the host. This technique connects the new storage system towhich data is to be migrated between the host computer and the oldstorage system from which the data is to be migrated. The data to bemigrated is moved from the old storage system to the new storage systemwhile the new storage system is receiving read/write requests for thedata from the host computer. When the new storage system has received aread/write request for data to be migrated which has not yet beenmigrated, the new storage system first issues a read request to the oldstorage system to migrate that data and then processes the read/writerequest after the data migration.

SUMMARY

When a new storage system is introduced, it may be desirable to continueto use some or all of the old storage system so as to effectivelyutilize all existing assets.

Further, as the capacity of storage systems has increased, the time ittakes to migrate data stored in them has tended to increase.

However, the above conventional technique does not consider how toutilize the old storage system after data migration. Therefore, the oldstorage system may need to be abandoned or used for a different purpose,for example.

Further, even though the above conventional technique allows the systemto be run without interruption while migrating data, the system loadincreases during the data migration since the data to be migrated isactually transferred from the old storage system to the new storagesystem, resulting in reduced system performance.

The present invention has been devised to solve the above problem. Itis, therefore, an object of the present invention to migrate data from asource storage system (or an old storage system) to a target storagesystem (or a new storage system) on a drive basis while receivingread/write requests for the data from the host computer and continuouslyusing some of the source storage system without directly transferringthe data from the source storage system to the target storage system.

The present invention provides a method for migrating from one storagesystem (a source storage system) to another storage system (a targetstorage system) in a computer system in which a host computer, thesource storage system, and the target storage system are connected toone another through a network. The host computer has running thereon amanagement program for switching between volumes of the source andtarget storage systems to selectively access one of the volumes. Thesource and target storage systems each include: a storage apparatus madeup of a disk drive(s); a storage control apparatus; a storage interfaceunit for connecting between the storage apparatus and the storagecontrol apparatus; and a host interface unit for connecting between thehost computer and the storage control apparatus. Each storage apparatushas a plurality of input/output ports which are connected with theinput/output ports of a respective storage interface unit, forming aninterface pair.

The method comprises the steps of: causing the management program on thehost computer to switch from a logical volume of the source storagesystem to a logical volume of the target storage system to access thelogical volume of the target storage system; defining a logical volumedefined on the storage apparatus (hereinafter referred to as “thestorage apparatus to be migrated”) in the source storage system as anexternal volume of the target storage system, and causing the hostcomputer to access the logical volume on the storage apparatus to bemigrated through the network as the external volume of the targetstorage system; connecting an input/output port of the storage interfaceunit in the target storage system with an input/output port of thestorage apparatus to be migrated; transmitting information on the diskdrive and the logical volume of the storage apparatus to be migrated tothe target storage system through the network; defining the logicalvolume on the storage apparatus to be migrated as a logical volume ofthe target storage system; causing the host computer to access the diskdrive of the storage apparatus to be migrated through the connectedinput/output ports as the logical volume of the target storage system;and blocking an input/output port of the storage apparatus to bemigrated, the input/output port being currently connected to aninput/output port of the storage interface unit in the source storagesystem.

Thus, the present invention migrates a storage apparatus in the sourcestorage system to the target storage system by causing the host computerto access the storage apparatus to be migrated as a storage apparatus ofthe target storage system.

The above disclosed arrangement allows the present invention to providea method for migrating data from a source storage system to a targetstorage system on a drive basis while receiving read/write requests forthe data from the host computer and continuously using some of thesource storage system without directly transferring the data from thesource storage system to the target storage system.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a diagram showing the configuration of a computer systemincluding storage systems according to a first embodiment of the presentinvention;

FIG. 2 is a diagram showing the internal configuration of the storagesystems according to the first embodiment of the present invention;

FIG. 3 is a diagram showing configuration management information 60 oneach component constituting a storage system 2;

FIG. 4A is a diagram showing logical volume management information;

FIG. 4B is a diagram showing drive group management information;

FIG. 4C is a diagram showing external volume management information;

FIG. 5 is a flowchart of a first process of a first method for migratingdata from a source storage system 2 a to a target storage system 2 b,wherein a drive enclosure 20 containing a drive 201 to be migrated ismigrated from the source storage system 2 a to the target storage system2 b together with all the drives 201 in the drive enclosure 20;

FIG. 6A is a first flowchart of a second process of the first method formigrating data from the source storage system 2 a to the target storagesystem 2 b, wherein the drive enclosure 20 containing the drive 201 tobe migrated is migrated from the source storage system 2 a to the targetstorage system 2 b together with all the drives 201 in the driveenclosure 20;

FIG. 6B is a second flowchart of the second process of the first methodfor migrating data from the source storage system 2 a to the targetstorage system 2 b, wherein the drive enclosure 20 containing the drive201 to be migrated is migrated from the source storage system 2 a to thetarget storage system 2 b together with all the drives 201 in the driveenclosure 20;

FIG. 7A is a first schematic diagram of the first method for migratingdata from the source storage system 2 a to the target storage system 2b, wherein the drive enclosure 20 containing the drive 201 to bemigrated is migrated from the source storage system 2 a to the targetstorage system 2 b together with all the drives 201 in the driveenclosure 20;

FIG. 7B is a second schematic diagram of the first method for migratingdata from the source storage system 2 a to the target storage system 2b, wherein the drive enclosure 20 containing the drive 201 to bemigrated is migrated from the source storage system 2 a to the targetstorage system 2 b together with all the drives 201 in the driveenclosure 20;

FIG. 8A is a first schematic diagram of a second method for migratingdata from the source storage system 2 a to the target storage system 2b, wherein the drive enclosure 20 containing the drive 201 to bemigrated and a drive interface 211 connected to the drive enclosure 20are migrated from the source storage system 2 a to the target storagesystem 2 b together with all the drives 201 in the drive enclosure 20;

FIG. 8B is a second schematic diagram of the second method for migratingdata from the source storage system 2 a to the target storage system 2b, wherein the drive enclosure 20 containing the drive 201 to bemigrated and the drive interface 211 connected to the drive enclosure 20are migrated from the source storage system 2 a to the target storagesystem 2 b together with all the drives 201 in the drive enclosure 20;

FIG. 9 is a flowchart of a third method for migrating data from thesource storage system 2 a to the target storage system 2 b, wherein thedrive enclosure 20 containing the drive 201 to be migrated and theinterface enclosure 21 connected to the drive enclosure 20 are migratedfrom the source storage system 2 a to the target storage system 2 btogether with all the drives 201 in the drive enclosure 20 and all thedrive interfaces in the interface enclosure 21;

FIG. 10A is a first schematic diagram of the third method for migratingdata from the source storage system 2 a to the target storage system 2b, wherein the drive enclosure 20 containing the drive 201 to bemigrated and the interface enclosure 21 connected to the drive enclosure20 are migrated from the source storage system 2 a to the target storagesystem 2 b together with all the drives 201 in the drive enclosure 20and all the drive interfaces in the interface enclosure 21;

FIG. 10B is a second schematic diagram of the third method for migratingdata from the source storage system 2 a to the target storage system 2b, wherein the drive enclosure 20 containing the drive 201 to bemigrated and the interface enclosure 21 connected to the drive enclosure20 are migrated from the source storage system 2 a to the target storagesystem 2 b together with all the drives 201 in the drive enclosure 20and all the drive interfaces in the interface enclosure 21;

FIG. 10C is a third schematic diagram of the third method for migratingdata from the source storage system 2 a to the target storage system 2b, wherein the drive enclosure 20 containing the drive 201 to bemigrated and the interface enclosure 21 connected to the drive enclosure20 are migrated from the source storage system 2 a to the target storagesystem 2 b together with all the drives 201 in the drive enclosure 20and all the drive interfaces in the interface enclosure 21;

FIG. 11 is a flowchart of a fourth method for migrating data from thesource storage system 2 a to the target storage system 2 b, wherein thedrive enclosure 20 containing the drive 201 to be migrated and theinterface enclosure 21 and the switches 222 in a controller enclosure 22which are connected to the drive enclosure 20 are migrated from thesource storage system 2 a to the target storage system 2 b together withall the drives 201 in the drive enclosure 20 and all the driveinterfaces in the interface enclosure 21;

FIG. 12A is a first schematic diagram of the fourth method for migratingdata from the source storage system 2 a to the target storage system 2b, wherein the drive enclosure 20 containing the drive 201 to bemigrated and the interface enclosure 21 and the switches 222 in thecontroller enclosure 22 which are connected to the drive enclosure 20are migrated from the source storage system 2 a to the target storagesystem 2 b together with all the drives 201 in the drive enclosure 20and all the drive interfaces in the interface enclosure 21;

FIG. 12B is a second schematic diagram of the fourth method formigrating data from the source storage system 2 a to the target storagesystem 2 b, wherein the drive enclosure 20 containing the drive 201 tobe migrated and the interface enclosure 21 and the switches 222 in thecontroller enclosure 22 which are connected to the drive enclosure 20are migrated from the source storage system 2 a to the target storagesystem 2 b together with all the drives 201 in the drive enclosure 20and the all the drive interfaces in the interface enclosure 21;

FIG. 12C is a third schematic diagram of the fourth method for migratingdata from the source storage system 2 a to the target storage system 2b, wherein the drive enclosure 20 containing the drive 201 to bemigrated and the interface enclosure 21 and the switches 222 in thecontroller enclosure 22 which are connected to the drive enclosure 20are migrated from the source storage system 2 a to the target storagesystem 2 b together with all the drives 201 in the drive enclosure 20and all the drive interfaces in the interface enclosure 21;

FIG. 13 is a flowchart of the processing procedure performed by readprograms 52 executed in the source storage system 2 a and the targetstorage system 2 b;

FIG. 14 is a flowchart of the processing procedure performed by writeprograms 53 executed in the source storage system 2 a and the targetstorage system 2 b;

FIG. 15 is a flowchart of the processing performed by a formattranslation program 55 executed in the target storage system 2 b;

FIG. 16 is a diagram showing the configuration of a computer systemincluding storage systems according to a second embodiment of thepresent invention; and

FIG. 17 is a diagram showing the configuration of a virtual managementnetwork apparatus.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

Preferred embodiments of the present invention will be described belowwith reference to FIGS. 1 to 17.

First Embodiment

A first embodiment of the present invention will be described below withreference to FIGS. 1 to 15.

A description will be given of the configuration of a computer systemincluding storage systems according to the first embodiment of thepresent invention with reference to FIG. 1.

FIG. 1 is a diagram showing the configuration of the computer systemincluding storage systems according to the first embodiment.

The computer system of the first embodiment is configured such thatstorage systems 2 are connected to a host computer 1 through a networkapparatus 3.

Specifically, a source storage system 2 a from which data is to bemigrated and a target storage system 2 b to which the data is to bemigrated are connected to the host computer 1 through the networkapparatus 3 during data migration operation, as shown in FIG. 1.

Further, the source storage system 2 a, the target storage system 2 b,the host computer 1, and the network apparatus 3 are all connected to amanagement terminal 4.

An application program 50 and a virtual management program 51 are loadedinto and executed by the host computer 1. The virtual management program51 has a function to, when the application program 50 has issued aread/write request for a volume, switch it with another volumetransparently to the application program 50 in order to support datamigration from the source storage system 2 a to the target storagesystem 2 b.

A description will be given below of the internal configuration of thestorage systems according to the first embodiment of the presentinvention with reference to FIG. 2.

FIG. 2 is a diagram showing the internal configuration of the storagesystems according to the first embodiment of the present invention.

Each storage system 2 (the source storage system 2 a and the targetstorage system 2 b) comprises a drive enclosure 20, an interfaceenclosure 21, a controller enclosure 22, and a maintenance terminal 23.

The drive enclosure 20 contains one or a plurality of disk drives 201,which are storage apparatuses. It should be noted that the first andsecond embodiments of the present invention will be described as appliedto storage apparatuses made up of magnetic disk drives. However, thefirst and second embodiments may be applied to storage apparatuses madeup of other types of recording disks such as optical disks, or otherrecording media such as flash memory and semiconductor disks.

Each drive 201 has a plurality of input/output ports. Further, eachstorage system 2 may include a plurality of drive enclosures 20.

The controller enclosure 22 contains a CPU package 220, a memory package221, and a plurality of switches 222 collectively constituting a storagecontrol unit. It should be noted that the controller enclosure 22 maycontain a plurality of CPU packages 220 and a plurality of memorypackages 221.

The CPU package 220 has therein a CPU, local memory, and a data transfercontrol unit.

A read program 52, a write program 53, a data migration program 54, aformat translation program 55, etc. are loaded into the local memory andexecuted.

Further, the memory package 221 has therein cache memory 223 and a datatransfer control unit.

The cache memory 223 relays data between the host computer 1 and eachdrive 201 so as to enhance performance.

The switches 222 are connected to host interfaces 210, drive interfaces211, and the CPU and the memory packages 220 and 221, and relay data tothem. Further, each switch 222 has an expansion port 224 for connectingwith a switch 222 in another controller enclosure 22 for data exchange,enabling a plurality of controller enclosures 22 to operate as a singlestorage control apparatus.

The interface enclosure 21 contains: the host interfaces 210 forcontrolling the data transfer between the host computer 1 and the cachememory 223; and the drive interfaces 211 for controlling the datatransfer between the cache memory 223 and each drive 201.

The host interfaces 210 receive read/write requests, etc. from the hostcomputer 1, as well as issuing read/write requests to another storagesystem 2. A pair of drive interfaces 211 is connected to theinput/output ports of each drive 201 in the drive enclosure 20.

Each host interface 210 and each drive interface 211 has thereininput/output ports, local memory, and a data transfer control unit.

It should be noted that the storage systems 2 may include a plurality ofinterface enclosures 21. Further, the host interfaces 210 and the driveinterfaces 211 may be set in different enclosures.

The maintenance terminal 23 is used to change the configuration of thestorage system 2 or check its internal state. Furthermore, it relaysinstructions from the management terminal 4 to the storage system 2. Themaintenance terminal 23 may be connected to the CPU package 220.

A description will be given below of data structures used by the storagesystems according to the present invention with reference to FIGS. 3 and4.

FIG. 3 is a diagram showing configuration management information 60 oneach component constituting a storage system 2. FIG. 4A is a diagramshowing logical volume management information. FIG. 4B is a diagramshowing drive group management information. FIG. 4C is a diagram showingexternal volume management information.

The configuration management information 60 indicates the states ofcomponents such as drive enclosures 20, drives 201 in each driveenclosure 20, interface enclosures 21, host interfaces 210 and driveinterfaces 211 in each interface enclosure 21, controller enclosures 22,the CPU package 220, memory package 221, and switches 222 in eachcontroller enclosure 22. Specifically, the configuration managementinformation 60 indicates whether each component is “implemented”,“unimplemented”, or “preliminarily implemented” which means that thecomponent is prepared for migration. Further, configuration informationon each drive 201 includes information for uniquely identifying thedrive, for example, information which can be obtained using the SCSI(Small Computer System Interface) Inquiry command, such as a vendor nameand a serial number.

Volumes in the storage systems 2 are managed in a hierarchical manner,and this information is stored in the cache memory 223.

The logical volume management information 61 includes, for each logicalvolume, a logical volume number, a logical volume capacity, a logicalvolume state, a host definition information list, a drive group number,and an external volume number, as shown in FIG. 4A.

It should be noted that a logical volume is a unit of storage area whicha storage system 2 provides to the host computer 1 and other storagesystems 2.

The logical volume number identifies the logical volume. The logicalvolume capacity is the capacity of the logical volume. The logicalvolume state is set to “normal”, “blocked”, or “not in use”. The hostdefinition information list includes information that allows the logicalvolume side to identify the host computer 1 which issues read/writerequests for the logical volume, such as the name of the host computer 1and port identifying information. The host definition information listalso includes information that allows the host computer 1 side toidentify the logical volume for which the host computer 1 issuesread/writes requests, such as port identifying information on thestorage system 2 and the LUN. The drive group number identifies eachdrive 201 in the storage system corresponding to the storage area (thelogical volume). The external volume number identifies a volume which isimplemented in another storage system 2 and corresponds to this logicalvolume.

When both the drive group number and the external volume number havebeen set, the logical volume can be accessed as not only a drive of thisstorage system 2 but also a volume of the another storage system 2 ifthe drive group and the external volume are both in a normal state.

The drive group management information 62 includes, for each drivegroup, a drive group number, a drive group capacity, a drive groupstate, a logical volume number, drive group attribute information, and adrive information list, as shown in FIG. 4B.

A drive group is a group of drives 201 (or a collection of the areas ofthese drives) and is used when distributing or storing data stored in alogical volume into a plurality of drives—by means of, for example, aRAID (Redundant Array of Independent Disks) technique.

The drive group number identifies the drive group. The drive groupcapacity is the capacity of the drive group. The drive group state isset to “normal”, “blocked”, or “not in use”. The drive group attributeinformation includes the corresponding logical volume number and RAIDconfiguration information (the RAID level, the number of data drives,the number of parity drives, the stripe size, etc.) The driveinformation list includes information on the area of each drive 201 inthe drive group, such as the drive number and capacity of the drive 201and the start address of its area.

The external volume management information includes, for each externalvolume, an external volume number, an external volume capacity, anexternal volume state, a logical volume number, external volumeattribute information, and an external volume access path list, as shownin FIG. 4C.

It should be noted that an external volume is actually a volume createdin another storage system but can be used by this storage system usingan external volume number.

The external volume number identifies the external volume. The externalvolume capacity is the capacity of the external volume. The externalvolume state is set to “normal”, “blocked”, or “not in use”. The logicalvolume number is the number of the logical volume corresponding to theexternal volume. The external volume attribute information includesinformation for uniquely identifying the external volume, such as theserial number of the another storage system and a volume number in theanother storage system. The external volume access path list includesinformation used to access the external volume, such as port identifyinginformation on this storage system and the another storage system andLUNs.

A description will be given below of a first method for migrating datafrom one storage system (a source storage system) to another storagesystem (a target storage system) according to the first embodiment ofthe present invention with reference to FIGS. 5 to 7.

FIG. 5 is a flowchart of a first process of the first method formigrating data from a source storage system 2 a to a target storagesystem 2 b, wherein a drive enclosure 20 containing a drive 201 to bemigrated is migrated from the source storage system 2 a to the targetstorage system 2 b together with all the drives 201 in the driveenclosure 20.

FIGS. 6A and 6B are flowcharts of a second process of the first methodfor migrating data from the source storage system 2 a to the targetstorage system 2 b, wherein the drive enclosure 20 containing the drive201 to be migrated is migrated from the source storage system 2 a to thetarget storage system 2 b together with all the drives 201 in the driveenclosure 20.

FIGS. 7A and 7B are schematic diagrams of the first method for migratingdata from the source storage system 2 a to the target storage system 2b, wherein the drive enclosure 20 containing the drive 201 to bemigrated is migrated from the source storage system 2 a to the targetstorage system 2 b together with all the drives 201 in the driveenclosure 20.

In the first process of the first method in which the drive enclosure 20containing the drive 201 to be migrated is migrated from the sourcestorage system 2 a to the target storage system 2 b together with allthe drives 201 in the drive enclosure 20, first a logical volume definedon the drive 201 to be migrated in the source storage system 2 a isdefined as an external volume of the target storage system 2 b, as shownin FIG. 5. Then, access by the host computer 1 to the logical volume onthe drive 201 to be migrated in the source storage system 2 a isreplaced by access to the external volume of the target storage system 2b; that is, the host computer 1 accesses the logical volume on the drive201 to be migrated as the external volume of the target storage system 2b, as shown in FIG. 7A(a).

Each step in FIG. 5 is executed from the management terminal 4, and thesource storage system 2 a and the target storage system 2 b each have adata migration program 54 running thereon.

First, the target storage system 2 b is connected to the networkapparatus 3 in step 501.

Then, in step 502, a setting is made in the source storage system 2 a soas to allow the target storage system 2 b to access the source storagesystem 2 a. It should be noted that when access by the target storagesystem 2 b to the source storage system 2 a is restricted by the networkapparatus 3, the setting of the network apparatus 3 also need to bechanged.

Then, the logical volume on the drive to be migrated in the sourcestorage system 2 a is defined as an external volume of the targetstorage system 2 b in step 503.

Specifically, the management terminal 4 sends port identifyinginformation on the source storage system 2 a, the LUN, etc. (which areused by the host computer 1 to access the source storage system 2 a) tothe target storage system 2 b as information on the logical volume ofthe drive to be migrated. The target storage system 2 b reserves a spacefor holding new external volume management information 63 and registersthe information received from the management terminal 4 with theexternal volume access path list. Furthermore, the target storage system2 b issues a request for information for identifying the volume to theLUN of the port of the source storage system 2 a accessed by the hostcomputer 1, and registers the obtained information as external volumeattribute information. The target storage system 2 b also makes aninquiry to the source storage system 2 a about the capacity of thevolume and registers it as an external volume capacity. Then, the targetstorage system 2 b sets the external volume state to “blocked”.

Then, in the target storage system 2 b, an empty logical volume isassigned to the logical volume on the drive to be migrated (which hasbeen defined as the external volume), and a path from the host computer1 is defined so as to allow the host computer 1 to access the volume, instep 504.

Specifically, Step 504 reserves a space for holding new logical volumemanagement information 61, sets the logical volume capacity and theexternal volume number, and stores information for identifying the hostcomputer 1, port identifying information for accessing the logicalvolume, the LUN, etc. with the host definition information list in orderto allow the host computer 1 to access the logical volume of the targetstorage system 2 b (the host computer 1 currently accesses the logicalvolume on the drive to be migrated in the source storage system 2 a).Furthermore, the states of the logical volume of the target storagesystem 2 b and the external volume to which the logical volume isassigned are set to “normal”.

Then, the virtual management program 51 switches the volume to beaccessed by the host computer 1 from the logical volume on the drive tobe migrated in the source storage system 2 a to the newly assignedlogical volume of the target storage system 2 b in step 505.

The virtual management program 51 switches these volumes transparentlyto the application program 50. When the application program 50 hasissued a request using the path at the time of switching the volumes,the request is processed according to the function of the virtualmanagement program 51 and the conditions under which the input/outputcommand from the application program 50 has been executed, as follows:

(1) Each request currently being processed is handled by the sourcestorage system 2 a, and a newly received request which has not yet beenprocessed is transferred to the target storage system 2 b.

(2) Each request currently being processed is handled by the sourcestorage system 2 a, and a newly received request which has not yet beenprocessed is held within the virtual management program 51. Then, afterall previous requests have been processed, the virtual managementprogram 51 switches the volumes to be accessed and transfers the heldnew request to the target storage system 2 b.

(3) The virtual management program 51 terminates all requests with anerror and then switches the paths so that the retried requests will beissued to the path to the target storage system 2 b.

Lastly, Step 506 invalidates the path definition from the host computer1 to the logical volume on the drive 201 to be migrated in the sourcestorage system 2 a and further invalidates the path definition to theother volumes (which are not targeted for data migration) on thedrive(s) 201 to be migrated, and then processing ends.

In the second process of the first method in which the drive enclosure20 containing the drive 201 to be migrated is migrated from the sourcestorage system 2 a to the target storage system together with all thedrives 201 in the drive enclosure, the drives 201 in the drive enclosure20 are disconnected from input/output ports of the drive interface inthe source storage system 2 a and then connected to input/output portsof the drive interface in the target storage system 2 b one afteranother. Then, after the above step, the drive enclosure 20 isreimplemented in the target storage system 2 b.

The present embodiment assumes that each drive in the drive enclosuresand each drive interface has a plurality of input/output ports. Thereason that each drive in the drive enclosures and each drive interfacehas a plurality of input/output ports is to employ a multiplexed path soas to enhance reliability.

Each step in FIGS. 6A and 6B is executed from the management terminal 4,and the source storage system 2 a and the target storage system 2 b eachhave a data migration program 54 running thereon.

First, the drive enclosure 20 containing the drive 201 to be migrated ispreliminarily implemented in the target storage system 2 b in step 601,as shown in FIGS. 6A and 7A(b). Specifically, step 601 reserves a spacefor holding new drive enclosure configuration information and sets thevalue “preliminarily implemented”. It should be noted that when aplurality of drive enclosures 20 are connected to the input/output portsof the drive interface 211 through which the drive to be migrated isaccessed, the above preliminary implementation operation is performed oneach of the plurality of drive enclosures 20 in order to migrate thesedrive enclosures 20 to the target storage system 2 b at the same time.

Then, in step 602, dirty data in the cache memory 223 is destaged to avolume(s) defined on each drive 201 in the drive enclosure 20 to bemigrated. It should be noted that dirty data is data in a cache memorywhich has not yet been saved, or written back, to the drive side; thatis, the data has not yet been reflected in the drive side. After theabove destaging process, the source storage system 2 a is instructed toswitch to “cache-through” operation (in which a data change is alwaysreflected in both the cache memory and a target drive).

The above step is performed to ensure the consistency of the data on thedrive to be migrated in steps 608 and 609 after read/write requests fromthe host computer 1 are processed.

Then, in the source storage system 2 a, one of the input/outputs port ofthe drive interface 211 connected to the drive enclosure 20 to bemigrated is blocked and thereby deimplemented in step 603, as shown inFIG. 7A(c).

The volume on the drive to be migrated can still be accessed through theother input/output port of the drive interface 211 which has not beenblocked.

Then, in step 604, one of the input/output ports of the drive interface211 of the target storage system 2 b is connected to the blockedinput/output port of the drive enclosure 20 to be migrated, forming apath through which the drive enclosure 20 can be accessed from the driveinterface 211, as shown in FIG. 7B(a). In the example shown in FIGS. 7Aand 7B, the drive interface 211 in the target storage system 2 b isprepared beforehand.

Then, each drive 201 in the drive enclosure 20 to be migrated ispreliminarily implemented in the target storage system 2 b in step 605,as shown in FIG. 7B(a). Specifically, step 605 reserves a space forholding new drive configuration information for each drive 201 to bepreliminarily implemented, obtains information for identifying the drive201, such as its manufacturer and serial number, and stores the obtainedinformation in a drive configuration information table. At this point,each drive 201 in the drive enclosure 20 to be migrated is fullyimplemented in the source storage system 2 a and preliminarilyimplemented in the target storage system 2 b.

Then, the source storage system 2 a transmits drive configurationinformation, logical volume management information 61, and drive groupmanagement information 62 on each drive 201 in the drive enclosure 20 tobe migrated to the management terminal 4 in step 606, as shown in FIG.7B(a).

The management terminal 4, in turn, transmits the received driveconfiguration information, logical volume management information 61, anddrive group management information 62 on each drive 201 to the targetstorage system 2 b.

Then, in step 607, the target storage system 2 b receives the driveconfiguration information, logical volume management information 61, anddrive group management information 62 on each drive 201 sent from themanagement terminal 4.

Then, in step 608, the target storage system 2 b associates eachpreliminarily implemented drive 201 with the drive configurationinformation transmitted from the source storage system 2 a through themanagement terminal (identifies each preliminarily implemented drive201), reserves a space for holding new drive group managementinformation 62, and creates the new drive group management information62 based on the drive group management information 62 obtained from thesource storage system 2 a. Specifically, the target storage system 2 bdetermines the drive group capacity, the drive group attributeinformation, and each start address and capacity in the driveinformation list based on the drive group management information 62obtained from the source storage system 2 a. Further, the target storagesystem 2 b sets the drive group state to “blocked”.

Further, in step 609, the target storage system 2 b associates thelogical volume of the target storage system 2 b corresponding to thelogical volume on the drive to be migrated with the correspondinglogical volume management information 61 obtained from the sourcestorage system 2 a (identifies the logical volume of the target storagesystem 2 b) and newly sets the drive group number in the logical volumemanagement information. The target storage system 2 b then sets thedrive group state in the drive group management information 62 to“normal”.

At this point, the source storage system 2 a has already startedcache-through operation on the volume defined on each drive 201 in thedrive enclosure 20 to be migrated. Therefore, even though the logicalvolume on the drive to be migrated in the source storage system 2 a isredefined as both an external volume and a volume on a preliminarilyimplemented drive group on the target storage system 2 b side andread/write operations are performed according to these two definitions,the data on the drive to be migrated can be made consistent with thecorresponding data in the cache memory in the target storage system 2 bby operating the data exclusively in the cache memory at the storagesystem 2 b, allowing the processing to be carried out withoutinterruption.

Referring now to FIG. 6B, in step 610, the target storage system 2 binvalidates the external volume definition of the logical volume definedon the drive 201 to be migrated (the external volume is associated witha logical volume of the target storage system 2 b), as shown in FIG.7B(b). Specifically, the target storage system 2 b deletes the externalvolume number from the logical volume management information 61 and setsthe (external volume) state in the external volume managementinformation 63 corresponding to the external volume number to “not inuse”.

Then, in step 611, the source storage system 2 a blocks and therebydeimplements the logical volume defined on each drive 201 in the driveenclosure 20 to be migrated. At this point, the drive to be migrated isaccessed based on the new drive group management information 62 set inthe target storage system 2 b.

Then, in step 612, the source storage system 2 a blocks and therebydeimplements the other one of the input/output ports of the driveinterface 211 connected to the drive enclosure 20 to be migrated.

Then, in step 613, the other input/output port of the drive interface211 in the target storage system 2 b is connected to the otherinput/output port (the blocked input/output port) of the drive enclosure20 to be migrated, forming a path through which the drive enclosure 20can be accessed from the drive interface 211, as shown in FIG. 7B(c).

Then, each drive 201 in the drive enclosure 20 to be migrated is fullyimplemented in the target storage system 2 b in step 614, as shown inFIG. 7B(d).

Then, the drive enclosure 20 to be migrated is deimplemented from thesource storage system 2 a in step 615, as shown in FIG. 7B(d).

Lastly, the drive enclosure 20 to be migrated is fully implemented inthe target storage system 2 b in step 616, as shown in FIG. 7B(d), andprocessing ends.

A description will be given below of a second method for migrating datafrom one storage system (a source storage system) to another storagesystem (a target storage system) according to the first embodiment ofthe present invention with reference to FIGS. 8A and 8B.

FIGS. 8A and 8B are schematic diagrams of the second method formigrating data from the source storage system 2 a to the target storagesystem 2 b, wherein the drive enclosure 20 containing a drive 201 to bemigrated and a drive interface 211 connected to the drive enclosure 20are migrated from the source storage system 2 a to the target storagesystem 2 b together with all the drives 201 in the drive enclosure 20.

It should be noted that the first method connects the drive enclosure 20to be migrated with the drive interface 211 prepared in the targetstorage system 2 b beforehand. The second method, on the other hand,migrates not only the drive enclosure 20 to be migrated but also thedrive interface 211 connected to the drive enclosure 20 to the targetstorage system 2 b; they are reimplemented and used in the targetstorage system 2 b.

It should be noted that the second method will be described belowfocusing on the differences from the first method and on important stepsfor migrating from the source storage system 2 a to the target storagesystem 2 b.

In this case, a pair of drive interfaces 211 (a drive interface pair)are connected to the drive enclosure 20 to be migrated, as in theconfiguration shown in FIG. 2. Further, each drive interface 211 isconnected to two switches 222, as shown in FIG. 8A.

As shown in FIG. 8A, the second method blocks an input/output port ofone of the pair of drive interfaces 211 (the input/output port beingcurrently connected to the drive enclosure 20) in step 603 shown in FIG.6A. The second method also disconnects the drive interface 211 from theswitches 222.

Then, the disconnected drive interface 211 is removed from the sourcestorage system 2 a and implemented in the target storage system 2 b.After that, as shown in FIG. 8B(b), an input/output port of theimplemented drive interface 211 is reconnected to the blocked(unconnected) input/output port of the drive enclosure to be migrated,forming a path. Furthermore, the implemented drive interface 211 isconnected to two switches 222 in the target storage system 2 b. Then,the second method performs steps similar to step 605 and later steps ofthe first method shown in FIG. 6A.

Thus, when the source storage system 2 a includes a plurality of driveinterfaces 211, one of them may be removed from the source storagesystem 2 a and reused in the target storage system 2 b.

A description will be given below of a third method for migrating datafrom one storage system (a source storage system) to another storagesystem (a target storage system) according to the first embodiment ofthe present invention with reference to FIGS. 9 and 10A to 10C.

FIG. 9 is a flowchart of the third method for migrating data from thesource storage system 2 a to the target storage system 2 b, wherein thedrive enclosure 20 containing the drive 201 to be migrated and theinterface enclosure 21 connected to the drive enclosure 20 are migratedfrom the source storage system 2 a to the target storage system 2 btogether with all the drives 201 in the drive enclosure 20 and all thedrive interfaces in the interface enclosure 21.

FIGS. 10A to 10C are schematic diagrams of the third method formigrating data from the source storage system 2 a to the target storagesystem 2 b, wherein the drive enclosure 20 containing the drive 201 tobe migrated and the interface enclosure 21 connected to the driveenclosure 20 are migrated from the source storage system 2 a to thetarget storage system 2 b together with all the drives 201 in the driveenclosure 20 and all the drive interfaces in the interface enclosure 21.

It should be noted that to migrate data from the source storage system 2a to the target storage system 2 b, the second method migrates the driveenclosure 20 to be migrated and a drive interface 211 connected to thedrive enclosure 20 to the target storage system 2 b together with allthe drives in the drive enclosure 20. The third method, on the otherhand, migrates the interface enclosure 21 containing the drive interface211 connected to the drive enclosure 20 together with all the driveinterfaces therein, instead of only the target drive interface 211.

It should be further noted that the third method will be described belowfocusing on the differences from the first and second methods and onimportant steps for migrating from the source storage system 2 a to thetarget storage system 2 b.

Unlike FIGS. 8A and 8B, FIGS. 10A to 10C show the interface enclosure 21to be migrated.

As shown in FIG. 10A, the third method blocks an input/output port ofone of the pair of drive interfaces 211 (the input/output port beingcurrently connected to the drive enclosure 20 to be migrated) in step603 shown in FIG. 6A. The third method also disconnects the driveinterfaces 211 from the switches 222. These steps are the same as thecorresponding steps of the second method.

However, unlike the second method, the third method does not remove thedisconnected drive interface 211 from the source storage system 2 a.Instead, the third method reconnects the blocked (disconnected)input/output port of the drive interface 211 to the blocked(disconnected) input/output port of the drive enclosure to be migratedand further connects the drive interface 211 to two switches 222 in thetarget storage system 2 b, forming a path, as shown in FIG. 10B.

Then, the interface enclosure 21 may be migrated to the target storagesystem 2 b after migrating the drive enclosure and each drive therein.

Thus, when the interface enclosure 21 in the source storage system 2 aconnected to the drive enclosure to be migrated contains a plurality ofdrive interfaces 211, some of them may be used to form a path throughwhich each drive in the drive enclosure to be migrated can be accessedfrom the target storage system 2 b. Then, the interface enclosure 21 maybe migrated to the target storage system 2 b after migrating each drive.

Each step in FIGS. 10A to 10C is executed from the management terminal4, and the source storage system 2 a and the target storage system 2 beach have a data migration program 54 running thereon.

First, the interface enclosure 21 to be migrated is preliminarilyimplemented in the target storage system 2 b in step 701.

Step 702 determines whether all drive interfaces 211 in the interfaceenclosure 21 to be migrated have been migrated from the source storagesystem 2 a to the target storage system 2 b.

If no (the NO branch from step 702), then a pair of drive interfaces211, the drive enclosure 20 connected the pair of drive interfaces 211,and each drive 201 in the drive enclosure 20 are migrated from thesource storage system 2 a to the target storage system 2 b in step 703.

The processing in step 703 is almost the same as that shown in FIGS. 6Aand 6B with the difference that in step 703, the drive interface 211deimplemented from the source storage system 2 a is used in the targetstorage system 2 b. Further, step 703 is different from thecorresponding step of the second method in that step 703 connects thedrive interface 211 to switches 222 in the target storage system 2 bwithout removing it from the interface enclosure 21.

That is, in the source storage system 2 a, an input/output port of oneof the pair of drive interfaces 211 is blocked (the input/output portbeing currently connected to the drive enclosure 20 to be migrated) andfurthermore the drive interface 211 is also disconnected from theswitches 222, as shown in FIG. 10A. Then, the drive interface 211deimplemented from the source storage system 2 a is connected to thedrive enclosure to be migrated again and further connected to switches222 in the target storage system 2 b without removing it from theinterface enclosure 21, as shown in FIG. 10B.

After that, the other drive interface 211 is disconnected from the driveenclosure to be migrated and switches in the source storage system 2 a,as shown in FIG. 10C.

It should be noted that the drive interface 211 deimplemented from thesource storage system 2 a may be connected to the target storage system2 b using the expansion ports of switches 222 in the controllerenclosure 22 of the target storage system 2 b. Processing then proceedsto step 704.

On the other hand, if all the drive interfaces 211 in the interfaceenclosure 21 to be migrated have been migrated from the source storagesystem 2 a to the target storage system 2 b (the YES branch from step702), then processing proceeds directly to step 704.

Then, in the source storage system 2 a, the host interfaces 210 in theinterface enclosure 21 to be migrated are blocked and therebydeimplemented in step 704.

After that, the interface enclosure 21 to be migrated is deimplementedfrom the source storage system 2 a in step 705.

Lastly, the interface enclosure 21 to be migrated is fully implementedin the target storage system 2 b in step 706, and processing ends.

A description will be given below of a fourth method for migrating datafrom one storage system (a source storage system) to another storagesystem (a target storage system) according to the first embodiment ofthe present invention with reference to FIGS. 11 and 12A to 12C.

Specifically, the fourth method migrates data from the source storagesystem 2 a to the target storage system 2 b in such a way that the driveenclosure 20 containing the drive 201 to be migrated and the interfaceenclosure 21 and the switches 222 in the controller enclosure which areconnected to the drive enclosure 20 are migrated from the source storagesystem 2 a to the target storage system 2 b together with all the drive201 in the drive enclosure 20 and all the drive interfaces in theinterface enclosure 21.

FIG. 11 is a flowchart of the fourth method for migrating data from thesource storage system 2 a to the target storage system 2 b, wherein thedrive enclosure 20 containing the drive 201 to be migrated and theinterface enclosure 21 and the switches 222 in the controller enclosure22 which are connected to the drive enclosure 20 are migrated from thesource storage system 2 a to the target storage system 2 b together withall the drive 201 in the drive enclosure 20 and all the drive interfacesin the interface enclosure 21.

FIGS. 12A to 12C are schematic diagrams of the fourth method formigrating data from the source storage system 2 a to the target storagesystem 2 b, wherein the drive enclosure 20 containing the drive 201 tobe migrated and the interface enclosure 21 and the switches 222 in thecontroller enclosure 22 which are connected to the drive enclosure 20are migrated from the source storage system 2 a to the target storagesystem 2 b together with all the drives 201 in the drive enclosure 20and all the drive interfaces in the interface enclosure 21.

Each step in FIG. 11 is executed from the management terminal 4, and thesource storage system 2 a and the target storage system 2 b each have adata migration program 54 running thereon.

First, the controller enclosure 22 to be migrated is preliminarilyimplemented in the target storage system 2 b in step 801.

Then, in the source storage system 2 a, one of the pair of switches 222in the controller enclosure 22 is blocked and thereby deimplemented instep 802, as shown in FIG. 12A(a). Since two switches are originallyimplemented in the controller enclosure 22 in each storage system 2, thesystem can continue to operate even after one of them is blocked.

Then, the blocked switch 222 is implemented in the target storage system2 b by connecting between the blocked switch 222 and a switch 222 of thetarget storage system 2 b through their expansion ports 224 in step 803,as shown in FIG. 12A(b).

Step 804 determines whether all interface enclosures 21 implemented forthe controller enclosure 22 to be migrated have been migrated from thesource storage system 2 a to the target storage system 2 b.

If no (the NO branch from step 804), then a pair of drive interfaces 211in each interface enclosure 21, the drive enclosure 20 connected to thepair of drive interfaces 211, and each drive 201 in the drive enclosure20 are migrated from the source storage system 2 a to the target storagesystem 2 b in step 805, as shown in FIG. 12B(a).

The processing in step 805 is almost the same as that shown in FIGS. 6Aand 6B with the difference that in step 805, the drive interface 211deimplemented from the source storage system 2 a is used in the targetstorage system 2 b, as in step 703 shown in FIGS. 8A and 8B.

It should be noted that the drive interface 211 deimplemented from thesource storage system 2 a may be connected to the target storage system2 b using the expansion ports 224 of switches 222 in the controllerenclosure 22 of the source storage system 2 a. Processing then proceedsto step 806.

On the other hand, if all interface enclosures 21 have been migratedfrom the source storage system 2 a to the target storage system 2 b (theYES branch from step 804), then processing proceeds directly to step806.

Then, as shown in FIG. 12B(b), all CPU packages 220, all memory packages221, and the other one of the pair of switches 222 in the controllerenclosure in the source storage system 2 a are blocked and therebydeimplemented in step 806, causing the source storage system 2 a tocease to operate.

Then, the other one of the pair of switches 222 in the controllerenclosure 22 to be migrated is implemented in the target storage system2 b in step 807, as shown in FIG. 12C(a).

Lastly, the controller enclosure 22 to be migrated is fully implementedin the target storage system 2 b in step 808, as shown in FIG. 12C(a).Then, the drive to be migrated is connected to a drive interface 211 inthe target storage system 2 b, and processing ends.

A description will be given below of the input/output operation of eachstorage system with reference to FIGS. 13 and 14.

Data stored in a storage system is read out by the read program 52loaded into the local memory in its CPU package. The read program 52 isexecuted by the CPU in the CPU package 220.

FIG. 13 is a flowchart of the processing procedure performed by the readprogram 52 executed in the source storage system 2 a or the targetstorage system 2 b.

First, the read program 52 receives a read request from the hostcomputer 1 or another storage system in step 901 and identifies thelogical volume targeted for the read operation in step 902.

Then, the read program 52 determines whether all read data is present inthe cache memory 223 in step 903.

If yes (the YES branch from step 903), then processing proceeds directlyto step 911.

If no (the NO branch from step 903), then in step 904 the read program52 determines whether the cache memory 223 space allocated to the readdata is too small to store all read data.

If the cache memory 223 space allocated to the read data is large enough(the NO branch from step 904), then processing proceeds directly to step906.

If, on the other hand, the cache memory 223 space allocated to the readdata is too small (the YES branch from step 904), then in step 905 anadditional memory space is allocated to the cache memory 223 to storeall read data.

Then, in step 906, the read program 52 determines whether the logicalvolume targeted for the read operation has been defined as an externalvolume which is currently in a normal state. That is, it is determinedwhether the logical volume management information 61 on the logicalvolume includes an external volume number and furthermore the externalvolume state in the external volume management information 63 includingthe same external volume number is set to “normal”.

If the logical volume targeted for the read operation has not beendefined as an external volume which is currently in a normal state (theNO branch from step 906), then the read program 52 identifies thecorresponding drive 201 based on the drive information list in the drivegroup management information 62 (on the drive group) corresponding tothe logical volume, and reads out the read data from it in step 907. Theread program 52 then stores the read data in the cache memory 223 instep 908. Processing then proceeds to step 911.

If the logical volume targeted for the read operation has been definedas an external volume which is currently in a normal state (the YESbranch from step 906), then the read program 52 transfers the readrequest to the external volume specified by the external volumemanagement information 63 associated with the logical volume in step909. The read program 52 then receives the read data from the anotherstorage system 2 for which the external volume has been defined, andstores the read data in the cache memory 223 in step 910. Processingthen proceeds to step 911.

It should be noted that if the logical volume has been associated withboth an external volume and a drive group which are currently in anormal state, the drive group may be accessed in preference to theexternal volume, which is not the case in steps 906 to 911. Further, theload on each access route may be measured when the read request has beenreceived and the access route under lower load conditions may beselected.

Then, the read data is transferred from the cache memory 223 to therequester for the read operation in step 911. Lastly, the read program52 sends a read request processing completion notification to therequester for the read operation in step 912, and then processing ends.

On the other hand, the read request transferred in step 909 is receivedby the source storage system 2 a for which the external volume has beendefined. The received read request is processed in the same manner as inthe above steps shown in FIG. 13. However, in the source storage system2 a, the drive group is selected to be accessed (the NO branch from step906), and the read data is read out from it in steps 907 and 908.

Data is written to a storage system by the write program 53 loaded intothe local memory in its CPU package. The write program 53 is executed bythe CPU in the CPU package 220.

FIG. 14 is a flowchart of the processing procedure performed by thewrite program 53 executed in the source storage system 2 a or the targetstorage system 2 b.

First, the write program 53 receives a write request from the hostcomputer 1 or another storage system 2 in step 1001 and identifies thelogical volume targeted for the write operation in step 1002.

Then, in step 1003, the write program 53 determines whether the cachememory 223 space allocated to the read data is too small to store allwrite data.

If the cache memory 223 space allocated to the read data is large enough(the NO branch from step 1003), then processing proceeds directly tostep 1005.

If, on the other hand, the cache memory 223 space allocated to the readdata is too small (the YES branch from step 1003), then in step 1004 anadditional memory space is allocated to the cache memory 223 to storeall write data.

Then, the requester for the write operation transfers the write data tothe cache memory 223 in step 1005.

Then, in step 1006, the write program 53 determines whether acache-through operation is performed on the logical volume targeted forthe write operation.

If no (the NO branch from step 1006), then the write program 53 issues awrite request processing completion notification to the requester forthe write operation in step 1007.

If yes (the YES branch from step 1006), then processing proceeds to step1008.

Then, in step 1008, the write program 53 determines whether the logicalvolume targeted for the write operation has been defined as an externalvolume which is currently in a normal state. That is, it is determinedwhether the logical volume management information 61 on the logicalvolume includes an external volume number and furthermore the externalvolume state in the external volume management information 63 includingthe same external volume number is set to “normal”.

If the logical volume targeted for the write operation has not beendefined as an external volume which is currently in a normal state (theNO branch from step 1008), then the write program 53 identifies thecorresponding drive 201 based on the drive information list in the drivegroup management information 62 (on the drive group) corresponding tothe logical volume, and writes the write data to it in step 1009.Processing then proceeds to step 1011.

If, on the other hand, the logical volume targeted for the writeoperation has been defined as an external volume which is currently in anormal state (the YES branch from step 1008), then in step 1010 thewrite program 53 writes the write data to the external volume specifiedby the external volume management information 63 associated with thelogical volume. Processing then proceeds to step 1011.

It should be noted that if the logical volume has been associated withboth an external volume and a drive group which are currently in anormal state, the drive group may be accessed in preference to theexternal volume, which is not the case in steps 1008 to 1010. Further,the load on each access route may be measured when the write request hasbeen received, and the access route under lower load conditions may beselected.

Lastly, in step 1011, the write program 53 determines whether acache-through operation is performed on the logical volume targeted forthe write operation in step 1011.

If no (the NO branch from step 1011), the write program 53 issues awrite request processing completion notification to the requester forthe write operation in step 1012, and then processing ends.

If yes (the YES branch from step 1011), then processing ends.

On the other hand (on the another storage system side, that is, thesource storage system 2 a side), the write request transferred in step1010 is received by the source storage system 2 a for which the externalvolume has been defined. The received write request is processed in thesame manner as in the above steps shown in FIG. 14. However, in thesource storage system 2 a, the drive group is selected to be accessed(the NO branch from step 1008), and the write data is written to it instep 1009. Further, the write request processing completion notificationis issued to the target storage system 2 b in step 1012.

A description will be given below of a method for converting redundantdata exchanged between the source storage system 2 a and the targetstorage system 2 b in such a way that data can be verified and correctedusing the redundant data even during a data migration process regardlessof the progress of conversion of the redundant data.

FIG. 15 is a flowchart of the processing performed by the formattranslation program 55 executed in the target storage system 2 b.

Redundant data is data added to each unit of data to be written to orread from a drive for data verification and correction purposes.

When the source storage system 2 a and the target storage system 2 bstore redundant data in different formats with real data, if the drive201 storing data to be migrated has been migrated from the sourcestorage system 2 a to the target storage system 2 b, the presentembodiment converts the format of the redundant data while receivingread/write requests for the data from the host computer 1.

The redundant data formats used by the source storage system 2 a and thetarget storage system 2 b may be different from each other, for example,when they employ different methods of calculating redundant data, orredundant data includes logical volume information on the source storagesystem 2 a.

The target storage system 2 b includes a format translation program 55which translates a redundant data format into another redundant dataformat and supports the redundant data format of the source storagesystem 2 a. Further, the drive group attribute information in the drivegroup management information 62 on each drive group includes: aredundant data format attribute for identifying a redundant data format;a “redundant data format translation in progress” flag for indicatingwhether or not the redundant data format is currently being translated;and a redundant data format translation pointer for indicating theprogress of translation of the redundant data format.

When, in step 608 shown in FIG. 6A, the target storage system 2 bcreates the new drive group management information 62 based on the drivegroup management information received from the source storage system 2 ain step 607, if the redundant data format attribute of the sourcestorage system 2 a is different from that of the target storage system 2b, the target storage system 2 b performs the following operations:setting the redundant data format attribute in the new drive groupmanagement information to that of the source storage system 2 a; settingthe “redundant data format translation in progress” flag to “ON”;initializing the redundant data format translation pointer (setting thestart address of the first drive in the drive information list); andactivating the format translation program 55. The format translationprogram 55 is executed by the CPU in the CPU package 220.

First of all, the format translation program 55 determines whether thereare any drive groups (management information 62) whose “redundant dataformat translation in progress” flag is set to “ON”, in step 1101.

If there are no drive groups whose “redundant data format translation inprogress” flag is set to “ON” (the NO branch from step 1101), thenprocessing ends.

If there are such drive groups (the YES branch from step 1101), theformat translation program 55 (selects one of them and) determineswhether the redundant data format of all drives listed in the driveinformation list (on the drive group) has been translated by comparingthe redundant data format translation pointer and the drive informationlist in step 1102.

If the data format of all drives has not yet been translated (the NObranch from step 1102), in step 1003 the format translation program 55reads out a certain amount of data from the location on a drive 201indicated by the redundant data format translation pointer and stores itin the cache memory 223 after verifying its validity according to theredundant data format of the source storage system 2 a.

Then, the format translation program 55 generates redundant data in theredundant data format of the target storage system 2 b from the readdata in step 1104.

After that, the format translation program 55 writes the data and thegenerated redundant data from the cache memory 223 to the drive 201 instep 1105.

Then, in step 1106, the redundant data format translation pointer isupdated by the amount of read data. If the redundant data formattranslation operation has reached the end of the (current) drive region(specified by the drive number, start address, and capacity of the driveindicated in the drive information list), then the format translationprogram 55 sets the redundant data format translation pointer at thestart address of the next drive in the drive information list andproceeds to step 1102.

If, on the other hand, the redundant data format of all the drives hasbeen translated (the YES branch from step 1102), in step 1107 the formattranslation program 55 updates the redundant data format attribute inthe drive group attribute information from the redundant data formatattribute of the source storage system 2 a to that of the target storagesystem 2 b. The data format translation program 55 then sets the“redundant data format translation in progress” flag of the currentdrive group to “OFF” in step 1108 and returns to step 1101.

This completes the description of the redundant data format translationprocess. In writing or reading data, the redundant data is used asfollows.

The read program 52 and the write program 53 perform the followingoperations in step 907 shown in FIG. 13 and in step 1009 shown in FIG.14, respectively. When the “redundant data format translation inprogress” flag in the drive group management information 62 on the drivegroup targeted for the read/write operation is set to “ON”, theseprograms check the redundant data format translation pointer to see ifthe redundant data format translation has already been completed on thedrive group targeted for the read/write operation. If so, they reads outthe redundant data according to the redundant data format of the targetstorage system 2 b. If not, they reads out the redundant data accordingto the redundant data format of the source storage system 2 a. Afterthat, these programs verify and correct the data using the redundantdata.

Second Embodiment

A second embodiment of the present invention will be described belowwith reference to FIGS. 16 and 17.

First, a description will be given of the configuration of a computersystem including storage systems according to the second embodiment ofthe present invention with reference to FIG. 16.

FIG. 16 is a diagram showing the configuration of the computer systemincluding storage systems according to the second embodiment of thepresent invention.

FIG. 17 is a diagram showing the configuration of a virtual managementnetwork apparatus.

According to the first embodiment, the host computer 1 has the virtualmanagement program 51 running thereon for switching between volumes toselectively access one of them.

According to the present embodiment, a virtual management networkapparatus 31 corresponding to the network apparatus 3 of the firstembodiment has a virtual management function to switch between a volumeon the virtual management network 31 side or the host side and a volumeon the storage system side.

The virtual management network apparatus 31 comprises a plurality ofinterfaces 32, a control module 33, control information memory 34, and aswitch 35. The switch 35 connects all the other components together.These components may be connected by any connecting method such as aswitch connection or bus connection. It should be noted that the controlinformation memory 34 is duplicated to ensure availability.

The interfaces 32 are connected to the host computer 1 and the storagesystems 2. The memory of each interface 32 stores input/outputmanagement information for managing read/write requests, data, statusinformation, etc., and transfer control information (inside and outsideof the virtual management network apparatus) for identifying theirtransfer destinations, etc.

The control module 33 is used to change the configuration of the virtualmanagement network apparatus 31 and monitor the internal conditions. Itshould be noted that the virtual management network 31 may be connectedto the management terminal 4, etc. and may operate according toinstructions from the management terminal 4 or another external device.

The control memory 34 stores exclusion information, storage systemvolume information, “virtual volume to storage system volume” mappinginformation, “host side volume to virtual volume” mapping information,etc.

The exclusion information is used to update the data stored in thecontrol memory 34 in an exclusive manner. The storage system volumeinformation is information on volumes of the storage systems 2 detectedby the virtual management network apparatus 31. The storage systemvolume information includes information specific to the storage systems2, address information, volume numbers, etc.

The “virtual volume to storage system volume” mapping information listseach detected storage system volume and the corresponding virtualvolume.

The “host side volume to virtual volume” mapping information is used tocontrol how each virtual volume appears to the host computer 1 (that is,how the host computer 1 accesses each virtual volume).

The host computer 1 can access each virtual volume associated with it bythe “host side volume to virtual volume” mapping information. To accessa virtual volume, first the host computer 1 transmits an access requestincluding host side volume identification information. Receiving thisaccess request, the virtual management network apparatus 31 checks the“host side volume to virtual volume” mapping information to determinethe virtual volume and then checks “virtual volume to storage systemvolume” mapping information to determine the storage system 2 and thevolume number (of the storage system volume) based on the identificationinformation included in the access request.

Then, the virtual management network apparatus 31 converts the accessrequest received from the host computer 1 into an access requestincluding the determined volume number (or identification information onthe determined volume) and transmits it to the determined storage system2.

When it is necessary to switch volumes to be accessed by the hostcomputer 1, the virtual management network apparatus 31 rewrites the“virtual volume to storage system volume” mapping information accordingto a volume switch instruction from the management terminal 4. That is,the virtual management network apparatus 31 changes the storage systemvolume associated with the virtual volume corresponding to the host sidevolume indicated by the virtual management network apparatus 31 to thehost computer 1 when the virtual management network apparatus 31 causesthe host computer 1 to access the logical volume on the drive to bemigrated. Specifically, the virtual management network apparatus 31switches from the logical volume on the drive to be migrated in thesource storage system 2 a to the logical volume of the target storagesystem 2 b which has been defined as an external volume for the logicalvolume on the drive to be migrated. With this arrangement, the virtualmanagement network apparatus 31 can cause the host computer 1 to accessthe logical volume on the drive to be migrated using the same host sidevolume identification information and the same virtual volumeidentification information even after switching from the source storagesystem 2 a to the target storage system 2 b. It should be noted that therewriting of the “virtual volume to storage system volume” mappinginformation and the transmission of an access request based on themapping information are carried out by programs in the memory of thevirtual management network apparatus 31 which are executed by the CPUwithin the virtual management network apparatus 31.

According to the present embodiment, step 504 in FIG. 5 registers thelogical volume of the target storage system 2 b which has been definedas an external volume for the logical volume on the drive to bemigrated, as storage system volume information. Further, step 505rewrites the “virtual volume to storage system volume” mappinginformation such that the storage system volume associated with thevirtual volume (corresponding to the host side volume indicated by thevirtual management network apparatus 31 to the host computer 1 when thevirtual management network apparatus 31 causes the host computer 1 toaccess the logical volume on the drive to be migrated) is changed fromthe logical volume on the drive to be migrated in the source storagesystem 2 a to the logical volume of the target storage system 2 b whichhas been defined as an external volume for the logical volume on thedrive to be migrated.

1. A computer system comprising: a host computer; a source storagesystem; and a target storage system; wherein said host computer, saidsource storage system, and said target storage system are connected toone another through a network; wherein said host computer has runningthereon a management program for switching between logical volumes ofsaid source and target storage systems to selectively access one of saidlogical volumes; wherein said source and target systems each include astorage apparatus, a storage control apparatus, a storage interface unitfor connecting between said storage apparatus and said storage controlapparatus, and a host interface unit for connecting between said hostcomputer and said storage control apparatus, said storage apparatushaving a first input/output port and a second input/output port forconnecting with said storage interface unit; and wherein to migrate saidstorage apparatus in said source storage system to said target storagesystem, said computer system performs the steps of: causing saidmanagement program to switch from a logical volume of said sourcestorage system to a logical volume of said target storage system toaccess said logical volume of said target storage system; defining alogical volume defined on said storage apparatus to be migrated in saidsource storage system as an external volume of said target storagesystem, and causing said host computer to access said logical volume onsaid storage apparatus to be migrated through said network and saidfirst input/output port of said storage apparatus to be migrated as saidexternal volume of said target storage system; connecting said secondinput/output port of said storage apparatus to be migrated with saidstorage interface unit in said target storage system, transmittinginformation on said logical volume on said storage apparatus to bemigrated to said target storage system, defining said logical volume onsaid storage apparatus to be migrated as a logical volume of said targetstorage system, and causing said host computer to access said logicalvolume on said storage apparatus to be migrated through said connectedsecond input/output port as said logical volume of said target storagesystem; and blocking said first input/output port of said storageapparatus to be migrated, said first input/output being currentlyconnected to said storage interface unit in said source storage system.2. The computer system as claimed in claim 1, wherein: said storagecontrol apparatus in said source storage system includes cache memory;and dirty data in cache memory is destaged to said storage apparatus tobe migrated before connecting said second input/output port of saidstorage apparatus to be migrated with said storage interface unit insaid target storage system, said dirty data having not yet been writtenback to said storage apparatus to be migrated.
 3. The computer system asclaimed in claim 1, wherein: said source storage system further includesa first storage interface unit and a second storage interface unit; andto migrate said storage apparatus to be migrated and said second storageinterface unit in said source storage system to said target storagesystem, said computer system performs the steps of: causing said hostcomputer to access said logical volume on said storage apparatus to bemigrated through said network and said first input/output port of saidstorage apparatus to be migrated as said external volume of said targetstorage system, said first input/output port being connected to saidfirst storage interface unit; blocking said second input/output port ofsaid storage apparatus to be migrated, said second input/output portbeing currently connected to said second storage interface unit in saidsource storage system; implementing said second storage interface unitin said target storage system, connecting said second storage interfaceunit with said second input/output port of said storage apparatus to bemigrated, and causing said host computer to access said logical volumeon said storage apparatus to be migrated through said secondinput/output port of said storage apparatus to be migrated as saidlogical volume of said target storage system; and blocking said firstinput/output port of said storage apparatus to be migrated.
 4. Thecomputer system as claimed in claim 3, wherein: said storage controlapparatus in said source storage system includes a first switch and asecond switch, and said storage control apparatus in said target storagesystem includes a switch; each switch is connected to said storageinterface units and has an expansion port for connecting andcommunicating with another switch; each storage apparatus is accessedthrough one or more switches of a storage control apparatus and one ormore storage interface units; said first switch is connected to saidfirst storage interface unit in said source storage system; said secondswitch is connected to said second storage interface unit in said sourcestorage system; and to migrate said storage apparatus to be migrated,said second storage interface unit, and said second switch of saidstorage control apparatus in said source storage system to said targetstorage system, said computer system performs steps of: causing saidhost computer to access said logical volume on said storage apparatus tobe migrated through said network, said first switch of said storagecontrol apparatus in said source storage system, and said first storageinterface unit as said external volume of said target storage system;blocking said second input/output port of said storage apparatus to bemigrated, said second input/output port being currently connected tosaid second storage interface unit in said source storage system;connecting said expansion port of said second switch with said expansionport of said switch of said storage control apparatus in said targetstorage system; implementing said second storage interface unit in saidtarget storage system, and connecting said second storage interface unitwith said second input/output port of said storage apparatus to bemigrated; and causing said host computer to access said storageapparatus to be migrated through said switch of said storage controlapparatus in said target storage system and said second switch of saidstorage control apparatus in said source storage system as a storageapparatus in said target storage system.
 5. The computer system asclaimed in claim 1, wherein: redundant data is added to data stored insaid storage apparatuses in said source and target storage systems toverify and correct said data; when the redundant data format of saidstorage apparatus in said source storage system is different from thatof said storage apparatus in said target storage system, redundant datain said logical volume on said storage apparatus to be migrated istranslated into said redundant data format of said storage apparatus insaid target storage system; and when said host computer accesses saidstorage apparatus to be migrated, said storage control apparatus in saidtarget storage system performs the steps of: verifying and correctingdata in said storage apparatus to be migrated according to saidredundant data format of said storage apparatus in said source storagesystem if redundant data for said data has not yet been translated intosaid redundant data format of said storage apparatus in said targetstorage system; and verifying and correcting said data in said storageapparatus to be migrated according to said redundant data format of saidstorage apparatus in said target storage system if said redundant datafor said data has already been translated into said redundant dataformat of said storage apparatus in said target storage system. 6.(canceled)
 7. (canceled)
 8. A method for migrating from a source storagesystem to a target storage system which are connected to a host computerthrough a network, said source and target storage systems eachincluding: a storage apparatus; a storage control apparatus; a storageinterface unit for connecting between said storage apparatus and saidstorage control apparatus; and a host interface unit for connectingbetween said host computer and said storage control apparatus; whereinsaid storage apparatus has a first input/output port and a secondinput/output port for connecting with said storage interface unit;wherein said host computer has running thereon a management program forswitching between volumes of said source and target storage systems toselectively access one of said volumes; and wherein said methodcomprises the steps of: (1) causing said management program to switchfrom a logical volume of said source storage system to a logical volumeof said target storage system to access said logical volume of saidtarget storage system; (2) defining a logical volume defined on saidstorage apparatus (hereinafter referred to as “said storage apparatus tobe migrated”) in said source storage system as an external volume ofsaid target storage system, and causing said host computer to accesssaid logical volume on said storage apparatus to be migrated throughsaid network and said first input/output port of said storage apparatusto be migrated as said external volume of said target storage system;(3) connecting said storage interface unit in said target storage systemwith said second input/output port of said storage apparatus to bemigrated; (4) transmitting information on said logical volume on saidstorage apparatus to be migrated to said target storage system; (5)defining said logical volume on said storage apparatus to be migrated asa logical volume of said target storage system, and causing said hostcomputer to access said logical volume on said storage apparatus to bemigrated through said connected second input/output port as said logicalvolume of said target storage system; and (6) blocking said firstinput/output port of said storage apparatus to be migrated, said firstinput/output port being currently connected to said storage interfaceunit in said source storage system.
 9. The method as claimed in claim 8,wherein: said storage control apparatus in said source storage systemincludes cache memory; and said method further comprises a step of:destaging dirty data in said cache memory to said storage apparatus tobe migrated before connecting said storage interface unit in said targetstorage system with said second input/output port of said storageapparatus to be migrated, said dirty data having not yet been writtenback to said storage apparatus to be migrated.
 10. A method formigrating from a source storage system to a target storage system whichare connected to a host computer through a network, said source andtarget storage systems each including: a storage apparatus; a storagecontrol apparatus; and a host interface unit for connecting between saidhost computer and said storage control apparatus; wherein said sourcestorage system further includes a first storage interface unit and asecond storage interface unit for connecting between said storageapparatus and said storage control apparatus in said source storagesystem; wherein said target storage system further includes a storageinterface unit for connecting between said storage apparatus and saidstorage control apparatus in said target storage system; wherein eachstorage apparatus has a plurality of input/output ports for connectingwith storage interface units; wherein said host computer has runningthereon a management program for switching between logical volumes ofsaid source and target storage systems to selectively access one of saidlogical volumes; and wherein said method comprises the steps of: (11)causing said management program to switch from a logical volume of saidsource storage system to a logical volume of said target storage systemto access said logical volume of said target storage system; (12)defining a logical volume defined on said storage apparatus (hereinafterreferred to as “said storage apparatus to be migrated”) in said sourcestorage system as an external volume of said target storage system, andcausing said host computer to access said logical volume on said storageapparatus to be migrated through said network and said firstinput/output port as said external volume of said target storage system,said first input/output port being connected to said first storageinterface unit; (13) blocking said second input/output port of saidstorage apparatus to be migrated, said second input/output port beingcurrently connected to said second storage interface unit in said sourcestorage system; (14) implementing said second storage interface unit insaid target storage system; (15) connecting said second storageinterface unit with said second input/output port of said storageapparatus to be migrated; (16) transmitting information on said logicalvolume on said storage apparatus to be migrated to said target storagesystem; (17) causing said host computer to access said logical volume onsaid storage apparatus to be migrated through said second storageinterface unit as a logical volume of said target storage system; and(18) blocking said first input/output port of said storage apparatus tobe migrated, said first input/output port being currently connected tosaid first storage interface unit.
 11. The method as claimed in claim10, wherein: said storage control apparatus in said source storagesystem includes a first switch and a second switch, and said storagecontrol apparatus in said target storage system includes a switch; eachswitch is connected to storage interface units and has an expansion portfor connecting and communicating with another switch; each storageapparatus is accessed through one or more switches of a storage controlapparatus and one or more storage interface units; said first switch isconnected to said first storage interface unit in said source storagesystem; said second switch is connected to said second storage interfaceunit in said source storage system; said (12) step causes said hostcomputer to access said logical volume on said storage apparatus to bemigrated through said network, said first switch of said storage controlapparatus in said source storage system, and said first storageinterface unit as said external volume of said target storage system;said method further comprises a step of, after said step (13),connecting said expansion port of said second switch with said expansionport of said switch of said storage control apparatus in said targetstorage system; and said (17) step causes said host computer to accesssaid storage apparatus to be migrated through said switch of saidstorage control apparatus in said target storage system and said secondswitch of said storage control apparatus in said source storage systemas a storage apparatus of said target storage system.
 12. The method asclaimed in claim 11, wherein: redundant data is added to data stored insaid storage apparatuses in said source and target storage systems toverify and correct said data; said method further comprises a step of,when the redundant data format of said storage apparatus in said sourcestorage system is different from that of said storage apparatus in saidtarget storage system, translating redundant data in said logical volumeon said storage apparatus to be migrated into said redundant data formatof said storage apparatus in said target storage system; and when saidhost computer accesses said storage apparatus to be migrated, saidstorage control apparatus in said target storage system performs thesteps of: verifying and correcting data in said storage apparatus to bemigrated according to said redundant data format of said storageapparatus in said source storage system if redundant data for said datahas not yet been translated into said redundant data format of saidstorage apparatus in said target storage system; and verifying andcorrecting said data in said storage apparatus to be migrated accordingto said redundant data format of said storage apparatus in said targetstorage system if said redundant data for said data has already beentranslated into said redundant data format of said storage apparatus insaid target storage system.
 13. (canceled)